Astigmatic testing device



-- y INVENTOR CHARLES sum/e0 BY Z TORNEY Dec. 8, 1925.

C. SHEARD ASTIGMATIC TESTING DEVICE Filed April 12. 1923 2 Sheets-Sheet 2 INVENTOR CHARLES SHE/1RD K TORNEY ings forming a part of Patented Dec. 8, 1925.

UNITED-STATES CHARLES snmm), or s'rummmon, MASSACHUSETTS, Assm'noa T0 AMERICAN 01 TION' OF MASSACHUSETTS.

TICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, VOLUNTARY ASSOCIA- ASTIGHATIC TESTING DEVICE.

Application filed April 12, 1923. Serial No. es1,52s.

To all whom it may concern:

Be it known that I, CHARLES SHEARD, a citizen of the United States, residing at Sturbrid ge, in the county of Worcester and State of Massachusetts, have invented certain new and usefulImprovements in As-- tigmatic Testing Devices,.of which the following is a specification.

This invention relates tov improvements in astigmatie testing devices.

' One object of the present invention is to produce an astigmatie testing dial from whidch the angle 'of astigmatism may be rea Another object is to produce. an'astig- 'matic testing dial which will test the visual acuity on two meridians disposed at right angles to one another. A further object is to produce sucha device of great sensitivity.

Otherobjects and advantages will be apparent from the following description taken in connection with the accompanying drawthis specification. f

In-the drawings: v Figure I is a front elevation of a device embodying the invention, parts being broken awa i Figure'II is a vertical transverse sectional view on the line 11-11 of Figure I.

Figure III is a detail perspective view of the rotatable plate. 4

Figure IV is an elevation of a modified form..

Figure V is a diagrammatic representation of the testing charts in use at the present time.

Figure VI is a view illustrating the a pearance of the rotatable plate when t e principal axes of astigmatism have been approximately found.

'Figure VII is a similar view when the correct meridians have been found.

Similar reference characters designate corresponding parts throughout the several views.

My device comprises essentially a cabinet I or casing 10 having'a front 11', which is provided with a central circular opening 12. Secured to the back-of the casing 10, and in central alignment withthe opemng is trast with the background.

mounted for rotation a bushing 14 carrying the bent arms 15, to the ends of which is secured a plate 16. The late 16 may be circular, as illustrated in igure I, and is slightly larger than the openin 12 in the front of the casing. The plate is provided with apertures17, said apertures being disposed in two-perpendicular meridians 18' and 19. On the. rear side of the plate covering the apertures 17, I provide a difi'using material 20, such as ground lass or tissue paper, and in the interior 0 the casing I provide suitable means for illumination, such as v illustrated at 21.

Surrounding the opening 12 is a suitably graduated dial 'havin angularindicia 22, with which tregisterindicating arrows 23 upon the rotatable plate 16, said arrows being in centralqalignment with the lines of aperturesl8 and 19. The connection betweenthebent arms 1 .5 and the plate 16 may be by rivets welding, or any other manner, but

I prefer to have it riveted, the-rivet on the outer side of the plate forming a thumb piece 24:. which .is convenient for rotating theflate. The front side of the plate 16 is pre erably painted jet black in order that the illuminated apertures 17 will properly contrast therewith.

The device may be modified as shown in Figure IV, wherein I have provided a dial 25 of any suitable sheet material, on which is rotatably mounted the plate 26 having painted thereon a series of geometricalfigures 27 herein shown as squares. In this construction the plate 26 and the dial '25 may be white and the squares 27 may be black, but I do not limit myself to black and white exclusively. If desired the plate 26 may be light pink or other color, and

the squares 2 of a suitable color to con- In both forms of the invention the squares 17 and .27 should be of equal size and the distance between the squares should be equal to the width of the squares; Squares are of such a size that they subtend an an le ofpne minute to a minute and a half for 51s distance at which the testis made. A series of rotatable plates may be furnished with each dial, each plate in the series having different sizes of squares for use in testing at various distances.

My device is preferably used in connection with the fogging system, which is well known to all refractionists. Under this system the patient is made artificially myopic by placing before the eye lenses of sufiicient positive power to produce this effect in all meridians. After the patients vision has been fogged adial, such as indicated inFigure V, is placed before him. This dial is provided with radiating lines 28 spaced approximately ten degrees'apart, the lines contrasting with the background upon which they appear. If the'condition of astigmatism exists, one of the lines 28 will appear more pronounced or clearer than all the others, the angularity of this line indicating the approximate axis of the astigmatism.

g The patie'ntis then placed before my improved dial and the plate. 16, or plate 26,

is revolved so that one of the lines 18, or

19, is disposed at the angle indicated by the patient in the preceding test. hen the principal axes of astigmatism have thus been found the apertures 17 will appear to be skewed or rhomboidal in form.. Then by slightly rotatingthe plate 16,.oneseries of apertures will seem to become a continuous line, while the other series of apertures will seem to become rectangular in shape,

as clearly shownirf Figure VII. Then this phenomenon is present the correct mer'diansof astigmatism have been found, after which.

the'proper cylindrical lens may be selected which will give equality of appearance to the two lines of squares.

From the foregoing it will'be evident that I have produced a new device for use in astigmatic testing, the device being extremely sensitive and a general improvement in the art. It is, of course, to be understood that Ido not limit myself to the precise details illustrated in the drawings, but may make changes falling within the scope of the claims without departing from the spirit of the invention. Having. thus described my invention, what I claim is:"

1. In a device of the character'described, a disc having two lines of separated squares crossing each other centrally of the disc,

'means for pivoting the disc at its center, a

circular scale surrounding the outer edges of the disc, and a pointer on the disc adapted to indicate on the scale the amount of movement of the diseabout its pivot.

2. In a device of the character described, a disc having two lines of perforated separated squares crossing each other centrally of the disc, means for pivoting the disc at its center, a circular scale surrounding the outer edges of the disc, a pointer on the disc adapted to indicate on the scale the movement of the disc about its pivot, and a light behind-the disc. p

3. In a device of the character described, a disc having two lines of separated squares crossing each other at right angles centrally of the disc,'brace members secured to the rear of the disc, a hub carried by the brace members,'and a member having a pivot pin adapted to fit in the hub, whereby the 'disc 

